Galaxy clusters are the largest structures in the Universe held together by gravity. Because of their immense size, their growth and evolution tell us a lot about how the Universe itself has changed over time. A newly discovered galaxy cluster provides some intriguing clues. This galaxy cluster is officially known as XDCP J0044.0-2033. Perhaps not surprisingly, astronomers decided to give a nickname to this mouthful of a cluster name. Because this cluster has many colors in X-ray light due to its plentiful hot gas and star forming galaxies, astronomers dubbed this the “Gioiello” Cluster, which means “Jewel” in Italian. The Gioiello Cluster is located about 9.6 billion light years from Earth. Scientists think this cluster formed approximately 3.3 billion years after the Big Bang. This means that the Gioiello Cluster is a mere 800 million years old as we observe it. A long observation from Chandra, totally over four days worth of observing time, provided astronomers with enough information to accurately determine the mass and other properties of the cluster. They found the Gioiello Cluster tops out at a whopping 400 trillion times the mass of the Sun. The discoveries of the Gioiello Cluster and others like it are helping astronomers better understand how galaxy clusters have developed over the lifetime of the Universe.
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Since NASA's Chandra X-ray Observatory was launched over 15 years ago, it has frequently turned its gaze to the center of the Milky Way galaxy. One of the reasons is that at the center of our Galaxy there is a black hole, which astronomers now estimate contains about four and a half million times the mass of the Sun. This makes this object, called Sagittarius A*, the closest supermassive black hole to us. Over the years, astronomers have learned many things about Sagittarius A* and it continues to surprise and intrigue scientists to this day. On September 13, 2013, astronomers saw a flare from Sagittarius A* that was 400 times brighter than its usual X-ray output. A little more than a year later, astronomers again used Chandra to see another flare from Sagittarius A* that was 200 times brighter than its normal state in October 2014.

What's going on with the Milky Way's biggest black hole? Astronomers have two theories about what could be causing these "megaflares" from Sagittarius A*. The first idea is that the intense gravity around the black hole ripped apart an asteroid that wandered too close. As the asteroid's debris swirled around the black hole, it would have been heated to temperatures that cause it to emit X-rays before passing over the edge of the black hole. The other proposed explanation involves the strong magnetic fields that exist around Sagittarius A*. If the magnetic field lines reconfigured themselves and reconnected, this could also create a large burst of X-rays. Scientists see flares happen regularly on the Sun and the events around Sgr A* appear to have a similar pattern in intensity levels to those. Whatever the final explanation is for these flares, scientists will continue to observe Sagittarius A* with Chandra and will undoubtedly make more fascinating discoveries about our Galaxy’s supermassive black hole.
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In fifteen years of operation, the Chandra X-ray Observatory has given us a view of the universe that is largely hidden from telescopes sensitive only to visible light.

Chandra has captured galaxy clusters - the largest gravitationally bound objects in the universe - in the process of forming, and provided the best evidence yet that the cosmos is dominated by a mysterious substance called dark matter.

Chandra has observed gas circling near a black hole's event horizon. The atoms of this gas are doomed to destruction by the extreme gravity of the black hole.

Most of the elements necessary for life are forged inside stars and blasted into interstellar space by supernovas. Chandra has tracked these elements with unprecedented accuracy.

Young stars are crackling with X-ray flares and other energetic radiation. By monitoring clusters of young stars, Chandra can give us a sense of what our young Sun was like when life was evolving on Earth.

Chandra: Taking us on a unique voyage into the big, bad and beautiful universe.
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Long before the term "citizen science" was coined, the field of astronomy has benefited from countless men and women who study the sky in their spare time. These amateur astronomers devote hours exploring the cosmos through a variety of telescopes that they acquire, maintain, and improve on their own. Some of these amateur astronomers specialize in capturing what is seen through their telescopes in images and are astrophotographers.

What happens when the work of amateur astronomers and astrophotographers is combined with the data from some of the world's most sophisticated space telescopes? These four composite images of galaxies reveal the possibilities. These galaxies are M101, also known as the "Pinwheel Galaxy", M81, Centaurus A, and M51, or, the "Whirlpool Galaxy". This Astro Pro-Am collaboration intends to raise interest and awareness among the amateur astronomer/astrophotographer community of the wealth of data publicly available, such as in NASA's various mission archives. This effort is particularly appropriate for this month because April marks Global Astronomy Month, the world's largest global celebration of astronomy.

For many amateur astronomers and astrophotographers, a main goal of their efforts is to observe and share the wonders of the Universe. However, the long exposures of these objects may also help to reveal phenomena that may otherwise be missed in the relatively short snapshots taken by major telescopes, which are tightly scheduled and often oversubscribed by professional astronomers. Therefore, projects like Astro Pro-Am might one day prove useful not only for producing spectacular images, but also contributing to the knowledge of what is happening in each of these cosmic vistas.
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In the middle of the twentieth century, an unusual star was spotted in the constellation of Canes Venatici (Latin for "hunting dogs"). Years later, astronomers determined that this object, dubbed AM Canum Venaticorum (or, AM CVn, for short), was, in fact, two stars. These stars revolve around each other every 18 minutes, and are predicted to generate gravitational waves - ripples in space-time predicted by Einstein.

Today, the name AM CVn represents a class of objects where one white dwarf star is pulling matter from a very compact companion star, such as a second white dwarf. (White dwarf stars are dense remains of Sun-like stars that have run out of fuel and collapsed to the size of the Earth.) The pairs of stars in AM CVn systems orbit each other extremely rapidly, whipping around one another in an hour, and in one case as quickly as 5 five minutes. By contrast, the fastest orbiting planet in our Solar System, Mercury, orbits the Sun once every 88 days.

Despite being known for almost 50 years, the question has remained: where do AM CVn systems come from? New X-ray and optical observations have begun to answer that with the discovery of the first known systems of double stars that astronomers think will evolve into AM CVn systems.

Observations with optical telescopes on the ground helped identify two systems, known as J0751 and J1741, that contain two white dwarfs and determined their masses. Scientists used Chandra to help rule out the possibility that J0751 and J1741 contained neutron stars. A neutron star - which would disqualify it from being a possible parent to an AM CVn system - would give off strong X-ray emission due to its magnetic field and rapid rotation. No X-ray emission was seen from either system, thus convincing scientists that these were going to evolve into AM CVn in the future.

As we mentioned before, AM CVn systems are of interest to scientists because they are predicted to be sources of gravitational waves. This is important because even though such waves have yet to be detected, many scientists and engineers are working on instruments that should be able to detect them in the near future. This will open a significant new observational window to the universe.
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When a massive star runs out fuel, it collapses and explodes as a supernova. Although these explosions are extremely powerful, it is possible for a nearby star to endure the blast. A team of astronomers using NASA's Chandra X-ray Observatory and other telescopes has found evidence for one of these survivors. This hardy star is in a stellar explosion's debris field - also called its supernova remnant - located in an HII region called DEM L241. An HII (pronounced "H-two") region is created when the radiation from hot, young stars strips away the electrons from neutral hydrogen atoms to form clouds of ionized hydrogen. This particular HII region is located in the Large Magellanic Cloud, a small neighboring galaxy to the Milky Way. The supernova remnant remains hot for thousands of years after the original explosion occurred, and this means that it continues to glow brightly in X-rays that can be detected by Chandra. The data suggest that a point-like source in X-rays is one component of a binary star system. In such a celestial pair, either a neutron star or black hole, which is formed when the star went supernova, is in orbit with a star much larger than our Sun. As they orbit one another, the dense neutron star or black hole pulls material away its companion star through the wind of particles that flows away from its surface. If this result is confirmed, DEM L241 would be only the third binary containing both a massive star and a neutron star or black hole ever found in the aftermath of a supernova.
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The Eta Carinae star system does not lack for superlatives. First, it contains one of the biggest and brightest stars in our galaxy, weighing at least 90 times the mass of the Sun. It is also extremely volatile and astronomers expect it will have at least one supernova explosion in the future. As one of the first objects observed by NASA's Chandra X-ray Observatory after its launch some 15 years ago, this double star system continues to reveal new clues about its nature through the X-rays it generates. New Chandra data are helping astronomers better understand how the two stars in Eta Carinae interact with one another through powerful winds blowing off their surfaces. As the two stars travel around each other in their elliptical orbits, the amount of X-rays detected changes. This gives astronomers clues to what is happening between these stars now and what may happen to this system in the future.
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Astronomers have made an important advance in the understanding of how clusters of stars like our Sun form using data from NASA's Chandra X-ray Observatory and infrared telescopes. The data show early notions of how star clusters are formed cannot be correct. The simplest idea is stars form into clusters when a giant cloud of gas and dust condenses. The center of the cloud pulls in material from its surroundings until it becomes dense enough to trigger star formation. This process occurs in the center of the cloud first, implying that the stars in the middle of the cluster form first and, therefore, are the oldest. These new results suggest something else is happening. By studying two clusters where Sun-like stars are forming - NGC 2024 (located in the center of the "Flame Nebula") and the Orion Nebula Cluster - researchers have discovered the stars on the outskirts of the clusters are actually the oldest. The researchers will use this same technique of combining X-rays and infrared data to study the age range in other clusters. In the meantime, scientists will be hard at work to develop other, more complex ideas to explain what they've seen in NGC 2024 and the Orion Nebula Cluster.
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Supernovas are the spectacular ends to the lives of many massive stars. These explosions, which occur on average twice a century in the Milky Way, can produce enormous amounts of energy and be as bright as an entire galaxy. These events are also important because the remains of the shattered star are hurled into space. As this debris field - called a supernova remnant - expands, it carries the material it encounters along with it. Astronomers have found a supernova remnant that is sweeping up a remarkable amount of material – equivalent to 45 times the mass of the Sun. This may indicate that a special type of stellar evolution has occurred, involving a giant star that ran into unusually dense material before exploding to form a supernova remnant. This supernova - which is called G352.7-0.1 -- has other interesting traits that scientists are still looking to explain. G352.7-0.1 is found about 24,000 light years from Earth in the Milky Way galaxy.
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Astronomers have found a remarkable object in our Milky Way galaxy. This object is a pulsar, the spinning dense core that remains after a massive star has exploded and collapsed. When this pulsar was created, something interesting happened because this pulsar is racing away from the supernova remnant where it was born at a speed between 2.5 million and 5 million miles per hour. This supersonic pace makes this pulsar - called IGR J1104-6103 -- one of the fastest moving pulsars ever observed. And what's more is that this runaway pulsar is leaving behind an extraordinary tail behind it as it goes. This tail is about 37 light years in length, making it the longest X-ray jet ever seen from an object in the Milky Way galaxy. New data from NASA's Chandra X-ray Observatory have been combined with radio data from the Australia Telescope Compact Array to provide astronomers with a more complete picture of what's happening in this system. For example, these data show that the tail has a distinct corkscrew shape. This suggests that the pulsar is wobbling like a top as it spins. IGR J1104-6103 is located about 60 light years away from the center of the supernova remnant SNR MSH 11-61A, which is where astronomers think the pulsar was originally created. By examining the details of the pulsar, its jet, and the supernova remnant, astronomers are piecing together the story of this exceptional object in our Galaxy.
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